Single stage to two stage compressor

ABSTRACT

A compressor includes a cylinder having major and minor compression chambers. The major compression chamber includes an ambient intake and an outlet which can be directed either to the intake of the minor chamber or directly to a holding tank. The outlet from the minor chamber is likewise directed to the gas storage tank. In a preferred embodiment, the compressor includes two cylinders each with a major and minor chamber operated by a three-lobed cam. The compressor switches from single stage to dual stage operation with valves operable in response to attaining a preset gas pressure in the holding tank or output.

BACKGROUND OF THE INVENTION

Multi-stage compressors act to compress air in a first chamber forcing it to a smaller second chamber and subsequently to an outlet. Thus, the piston in the smaller chamber is compressing already compressed air. This allows the compressor to achieve higher pressures. However, such operation is volumetrically inefficient at lower pressures.

SUMMARY OF THE INVENTION

The present invention is premised on the realization that the efficiency of a compressor can be improved by switching from a single stage compressor having major and minor compression chambers to a two stage or dual stage compressor. The output from the larger major chamber is switched between either an outlet such as to a holding tank or to the intake of the smaller minor chamber which is in turn connected to an outlet and subsequently the holding tank. This allows for initial operation of the compressor in a single stage mode wherein the outputs from both the major and minor compression chambers are directed to a holding tank. When a predetermined pressure is achieved, the output from the major chamber is directed to the intake to the minor chamber, thus switching to a two stage compressor and allowing for greater pressures.

This maximizes the efficiency of the compressor allowing it to maximize volumetric output initially and, subsequently, maximize pressure output.

The present invention is described with respect to a three-lobed cam-operated dual-piston compressor which provides many advantages for the present invention. However, other compressor designs with more than one compression chamber will function in the present invention. A three lobed cam-operated dual piston compressor is shown in U.S. patent application Ser. No. 11/235,884, entitled ROTARY TO RECIPROCAL POWER TRANSFER DEVICE, filed on Sept. 25, 2005, the disclosure of which is hereby incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of the present invention;

FIG. 2A is a cross sectional view of the present invention in a single stage mode with the pistons in a first stroke position;

FIG. 2B is a cross sectional view of the present invention in a single stage mode with the pistons in a second stroke position;

FIG. 3A is a cross sectional view of the present invention in a dual stage mode with the pistons in a first stroke position;

FIG. 3B is a cross sectional view of the present invention in a two-stage mode with the pistons in a second stroke position.

FIG. 4 is an exploded perspective view of the follower of the present invention, partially broken away.

DETAILED DESCRIPTION OF THE INVENTION

As shown, the compressor 10 includes an exterior housing 18. Housing 18 includes a circular peripheral wall 24 and two side walls 26 and 28. First and second cylindrical mounts 20 and 22, located on peripheral wall 24, support the first and second compressor chambers 14 and 16. A shaft 30 extends through walls 26 and 28 and is fixed to cam 12. The cam 12, when rotated by shaft 30, moves a follower 34 which, in turn, causes reciprocation of first and second pistons 36 and 38.

Cam 12 rotates within the follower 34 which includes a body portion 48 (see FIG. 4) formed from first and second spaced body members 50 and 52 on either side of cam 12. The first and second members 50 and 52 each include slots 54, 56 aligned with a central axis 58 of device 10. The follower 34 has dogleg portions 55 and 57, which are oppositely offset from central axis 58. The follower 34 further includes first and second head portions 60 and 62 which hold the body members 50 and 52 together on either side of cam 12. First and second rollers 64 and 66 are mounted to head portions 60 and 62. Also fixed to head portions 60 and 62 are first and second rods 68 and 70 which, in turn, attach to the first and second pistons 36 and 38, respectively.

The dogleg portions 55 and 57 and follower 34 are directed toward the driving surface of the cam 12, and opposite the direction of arrows 46.

As shown in FIG. 4, first head portion 60 is resiliently mounted to the first and second members 50 and 52 of the follower body, whereas second head portion 62 is fixedly attached to first and second members 50 and 52.

The first head portion 60 includes a top surface 72 and first and second legs 74 and 76. The first roller 64 is attached to the first head 60 by a pin 78 which extends through first and second legs 74 and 76. The head portion 60 is mounted to first and second members 50 and 52 with four hex screws 80 which run through axially stepped bores 82. Shaft 84 of screws 80 extend through a resilient member which, as shown, is a series of Belleville washers 86 and a sleeve 88 and fastens to members 50 and 52 of the follower body 48. The Belleville washers rest on a shoulder 90 secured by head 91 of screw 80. Any suitable resilient member, such as a spring or the like, can be used in place of the Belleville washer.

The second head 62 can be a mirror image of first head 60, or, as shown, is simply a C-shaped cap with legs 92 and 93 attached with screws 81 to the members 50 and 52 of follower body 48. The rods 68 and 70 are bolted to heads 60 and 62 at one end 61 and are attached to cylinders 36 and 38 at the opposite end.

Compression chambers 14 and 16 are cylindrical which house pistons 36 and 38. Rods 68 and 70 extend into chambers portion 14 and 16 through bushings 94,95 and oil seals 96,97 in circular plates 98,99 of discs 100,101. Chambers 14 and 16 fit within discs 100, 101 forming sealed cylindrical chambers.

Compression chamber 14 includes major and minor (by volume) compression chambers 125 and 126 separated by piston 36. Likewise, compression chamber 16 includes major and minor compression chambers 127 and 128 separated by piston 38. Compression chambers 14 and 16 also include intakes 104, 105, 106, and 107, and exhausts 108, 109, 110 and 111 leading to and from the respective major and minor compression chambers. Each of these intakes and exhausts utilizes flap valves 112 to allow air or gas in or out of the respective chambers.

The exhaust output lines 108 and 109 lead from the minor compression chambers 128 and 126 directly to a holding tank 113. These could lead to any output connected to the compressor. Further, intakes 106 and 107 lead from the ambient environment (or any source of low pressure gas) to the major compression chambers 125 and 127. Exhaust line 110 leads from major compression chamber 125 to valve 114, and exhaust line 111 leads from major compression chamber 127 to valve 116.

As shown in FIGS. 2A, 2B, 3A and 3B, the valve 114 and 116 can direct intake air for intake 104 and 105 respectively, either from the exhaust lines 110 and 111 or from the ambient intakes 118 and 120. When inlets 104 and 105 are receiving intake airfrom ambient intakes 118 and 120, the exhaust from lines 110 and 111 are directed through lines 122 and 124 to the holding tank 113. Valves 114 and 116 are in turn controlled by a pressure sensor (not shown) located in the holding tank 113. The pressure sensor will enable pre-set pressure switching of valves 114 and 116.

In operation, the shaft 30 will rotate, causing the cam 12 to rotate. The action of the cam 12 against rollers 64 and 66 causes the follower 34 to move in the direction of arrow 102 as shown in FIG. 2A and, subsequently, in the direction of arrow 103 shown in FIG. 2B. This will in turn cause the rods 68 and 70 and associated cylinders 36 and 38 to move in the direction of arrow 102 and, subsequently, 103. In the single stage operation, as shown in FIG. 2A, with the follower fully extended in the direction of arrow 102 the piston 38 will be in an extended position as shown in FIG. 2A with piston 36 in a retracted position. As these pistons move, gas from chamber 125 will be directed through exhaust 111 through line 124 to holding tank 113. Gas will be drawn into chamber 126 from intake line 120 into line 105. Likewise, as the cylinder 36 moves in the direction of arrow 102, gas will be drawn through intake 106 into chamber 127. Gas in chamber 128 will be forced through exhaust 108 directly to holding tank 113.

As pistons 36 and 38 move in the direction of arrow 103, the gas in chamber 125 is forced through exhaust 110 to holding tank 113. Gas will be drawn in through intake 107 to fill chamber 127. Likewise, gas will be directed from intake 118 through line 104 into chamber 126, and gas from chamber 128 will be forced through line 111 through valve 116 and line 124 to the holding tank 113.

If a pre-determined pressure is sensed in the holding tank or output lines, valves 114 and 116 switch to the positions shown in FIGS. 3A and 3B. As shown in FIG. 3A, with the pistons 36 and 38 moving in the direction of arrow 102, the compressed air from major chamber 127 will be driven through exhaust 111 through valve 116 to intake line 105 and into minor chamber 128. Piston 36 will draw gas into chamber 125 through intake 106 and direct gas from minor chamber 126 through exhaust line 108 to holding tank 113. When the pistons move in the direction of arrow 103, gas will be drawn in through intake 107 into major chamber 127 and the gas in minor chamber 128, which previously was directed from chamber 127, will go directly to holding tank 113 through line 109. Piston 36, in turn, will force compressed gas from major chamber 125 through exhaust line 110 and valve 114 through intake line 104 into minor chamber 126. Thus, in this embodiment, the gas initially is taken into major, or larger, chambers 125 and 127, forced into minor, or smaller, chambers 126 and 128, respectively, and, subsequently, compressed again forcing it into holding tank 113.

In the first mode of operation, the compressor 10 pumps the largest volume of gas with output from all four chambers 125, 126, 127, 128 directed to the holding tank to fill the holding tank 113 with gas as rapidly as possible. Once the tank reaches a pre-determined pressure, the valves 114 and 116 will be switched to the position shown in FIGS. 3A and 3B, which will allow gas at a higher pressure and lower volume to be forced into holding tank 113. Because the chambers 126 and 128 are smaller than chambers 125 and 127, the air introduced in this mode into chambers 126 and 128 will be compressed, as opposed to ambient pressure, which will then be again compressed further when forced into the holding tank. This allows for higher pressure operation.

Due to the design of this pump, only two valves are required, switching from one mode to a second mode. Further, these valves operate automatically in response to a preset pressure.

Because the compressor is set up for operation in both directions of piston movement, both pistons 36 and 38 will be compressing gas regardless of the direction of movement of the pistons 36 and 38.

In this design, the oil seals 96,97 must also provide the compression seals for the minor chambers in addition to preventing oil in the housing 18 from entering the cylinders 14,16. This allows the compressor cylinders 14,16 to operate without oil. This eliminates the need for any type of oil removal equipment downstream from the compressor in applications where the presence of oil cannot be tolerated.

This has been a description of the present invention along with the preferred method of practicing the present invention. However, the invention itself should only be defined by the appended claims, WHEREIN 

1. A compressor having a major compression chamber and a minor compression chamber, and a piston operable in said compressor and dividing said major and minor chambers an inlet into said major chamber; an inlet into said minor chamber; an outlet from said major chamber; an outlet from said minor chamber leading to a compressed gas storage container; a valve configured to connect said outlet from said major chamber to alternately said inlet to said minor chamber and said compressed gas storage container.
 2. The compressor claimed in claim 1 wherein said valve is actuated by a preset output pressure.
 3. The compressor claimed in claim 2 wherein said major and minor chambers are in a cylinder divided by said piston.
 4. The compressor claimed in claim 1 including first and second cylinders having first and second major and first and second minor chambers and a second valve, said second valve configured to connect said outlet from said second major chamber to alternately said inlet to said second minor chamber or said compressed gas storage container.
 5. The compressor claimed in claim 4 wherein said compressor is a rotary cam operated compressor.
 6. The compressor claimed in claim 5 comprising a multi-lobed rotating cam; a follower having two bearing surfaces riding on said cam, said follower movable back and forth along a first axis; said follower having first and second ends fixed to said first and second pistons, said first and second ends being oppositely offset from said first axis wherein said pistons are movable on second and third axes which are offset and parallel to said first axis.
 7. The compressor claimed in claim 6 wherein said follower includes a central body portion with first and second oppositely extended doglegs.
 8. The compressor claimed in claim 6 wherein said cam is a three-lobed cam. 